[ros-users] gazebo joint parameters

[John Hsu]

I suggest start by making sure the mass and moment of inertias are close to
realistic values.  Then to get rid of the smooth-slow motion you are seeing,
slowly increasing damping coefficients for the joints.  Unfortunately,
realistic damping coefficients are hard to come by, and for PR2 we got them
by simply trying out different values and comparing joint responses when
given a joint trajectory command.  Note that when damping coefficient is too
large, the joint may become unstable, at that point, you can optionally
reduce time stepping size or increase quickStepW in your world file.
John

On Thu, Aug 5, 2010 at 9:35 AM, Ugo Cupcic <ugo at shadowrobot.com> wrote:

>  Hi John,
>
> Ok. I'm having trouble getting a realistic behaviour for my model in
> gazebo... It acts really really smoothly, with really slow movements when
> I'm not sending commands to it. For example when the hand hasn't received
> any command yet, it will close its fingers in maybe 10 seconds as if it were
> in oil or something.
>
> Any idea on how to improve this?
>
> Cheers
>
>
> On 05/08/10 17:30, John Hsu wrote:
>
> Hi Ugo,
> Friction is not modeled in ode at this point, if it's something you need,
> please file a feature request ticket here<https://code.ros.org/trac/ros-pkg/newticket>,
> and set simulator_gazebo as the component.  Modeling coulomb friction at a
> joint is possible in ODE, but has not been tested.
> thanks,
> John
>
> On Thu, Aug 5, 2010 at 5:13 AM, Ugo Cupcic <ugo at shadowrobot.com> wrote:
>
>>  Thanks a lot. I missed this!
>>
>>
>> On 05/08/10 13:11, Adolfo Rodríguez Tsouroukdissian wrote:
>>
>>
>>
>> On Thu, Aug 5, 2010 at 1:17 PM, Ugo Cupcic <ugo at shadowrobot.com> wrote:
>>
>>>  Hi all,
>>>
>>> I'm currently trying to get a better control on our gazebo model of the
>>> Hand. I'm having trouble finding any kind of documentation regarding the
>>> parameters you can apply to a joint (e.g. friction). Is there a place I
>>> could start with?
>>>
>>> For the time being, my joints look like this:
>>>  <joint name="trunk_rotation" type="revolute">
>>>      <parent link="${parent}"/>
>>>      <child link="shadowarm_trunk"/>
>>>      <origin xyz="0 0 0.01" rpy="0 0 0" />
>>>      <axis xyz="0 0 1" />
>>>      <limit lower="-${M_PI/2}" upper="${M_PI/4}"
>>>      effort="10" velocity="1.0"/>
>>>      <dynamics damping="1"/>
>>>  </joint>
>>>
>>>  You can add static friction to the dynamics joint element. This link
>> documents all the valid elements for a URDF joint:
>>
>>  http://www.ros.org/wiki/urdf/XML/Joint
>>
>> HTH
>>
>> Adolfo
>>
>>
>>> Cheers,
>>>
>>> Ugo
>>>
>>> --
>>> Ugo Cupcic         |  Shadow Robot Company | ugo at shadowrobot.com
>>> Software Engineer  |    251 Liverpool Road |
>>> need a Hand?       |    London  N1 1LX     | +44 20 7700 2487
>>> http://www.shadowrobot.com/hand/              @shadowrobot
>>>
>>> _______________________________________________
>>> ros-users mailing list
>>> ros-users at code.ros.org
>>> https://code.ros.org/mailman/listinfo/ros-users
>>>
>>
>>
>>
>> --
>> Adolfo Rodríguez Tsouroukdissian, Ph. D.
>>
>> Robotics engineer
>> PAL ROBOTICS S.L
>> http://www.pal-robotics.com
>> Tel. +34.93.414.53.47
>> Fax.+34.93.209.11.09
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>>
>> --
>> Ugo Cupcic         |  Shadow Robot Company | ugo at shadowrobot.com
>> Software Engineer  |    251 Liverpool Road |
>> need a Hand?       |    London  N1 1LX     | +44 20 7700 2487http://www.shadowrobot.com/hand/              @shadowrobot
>>
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>
>
> --
> Ugo Cupcic         |  Shadow Robot Company | ugo at shadowrobot.com
> Software Engineer  |    251 Liverpool Road |
> need a Hand?       |    London  N1 1LX     | +44 20 7700 2487http://www.shadowrobot.com/hand/              @shadowrobot
>
>
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